The present invention relates, in general, to injection molding machines and, in particular, to a new and useful mold locking arrangement having a thermal force control feature.
In injection molding machines, for example, for light metals or plastics, special, mostly complicated constructual provisions are necessary to keep the magnitude and direction of the forces exerted through a tie rod supporting the mold parts constant, for example, or to control them in a desired way. For example, in injection molding machines for plastics equipped with a toggle mold-locking mechanism in which the locking force must be taken up by a plurality of tie rods, these rods are submitted to strain or bending by which the locking force acting on the mold parts is varied. In addition, unequal variations in length, or bending, of the different tied rods may cause an unsymmetrical distribution of the locking force over the parting surfaces of the mold. There are mechanically or hydraulically operated centralized adjusting devices known by means of which the locking force of such machines can be adjusted, or controlled, automatically. Such devices are relatively inaccurate in operation and make no allowance for inevitable wear. Also, the prior art constructions for controlling the locking force are particularly expensive.